大跨隧道拱盖法施工地层沉降分析

针对"上软下硬"地层中大跨隧道拱盖法施工的地层沉降问题,选取某地铁车站的典型剖面,建立二维分步开挖模型,通过分步开挖全过程的数值分析,得到拱盖法不同施工步序下的沉降值,推断控制重要环节为中导洞开挖、拆撑和拱盖施作、侧导洞开挖。对重要工序下地表沉降监测值进行对比分析,进一步对各阶段沉降比重进行验证,并分析两者发生偏差的原因并提出相应对策。

Analysis on Ground Settlement during Construction of Large-span Tunnel with Arch Cover Method

Focusing on the problem of ground settlement during construction of large-span tunnel by arch cover method in the strata where the upper rock soil is soft and the lower rock soil is rigid,the paper established a two-dimensional model of multi-step excavation of the typical sections of a certain metro station. And then,by means of numerical analysis on the whole process of multi-step excavation,the settlement values with arch cover method under several construction procedures were obtained. On this basis,the paper suggested that the key procedures which should be under control were the excavation of middle pilot heading,the removal of temporary support,the erection of arch cover,and the excavation of lateral pilot heading. Furthermore,comparative analysis on ground settlement of key procedures was made in this paper,and the settlement proportion of every procedure was verified further. After analyzing the probable reason for the difference between monitoring value and simulation value,the corresponding countermeasures were proposed.